Advances in technology have resulted in smaller and more powerful computing devices. For example, there currently exist a variety of portable computing devices, including wireless computing devices such as wireless telephones, personal digital assistants (PDAs), and tablet computers that are small, lightweight, and easily carried by users. In order to simplify user interfaces and to avoid pushbuttons and complex menu systems, such portable computing devices may use touch screen displays that detect user gestures on the touch screen and translate the detected gestures into commands to be performed by the device. Such gestures may be performed using one or more fingers or a stylus type pointing implements in contact with or in close proximity to a sensing surface. The term Quality-of-Service (QoS) is collectively used to represent several properties of touch screen implementations such as position update rate, accuracy of determined touch position, touch position determination resolution, the maximum number of objects tracked simultaneously, usage modalities such as contact or contact-less operation, detection sensitivity, etc.
Touch sensing function is heavily impacted by environmental factors like conducted or radiated electromagnetic noise, temperature, humidity, etc. Electromagnetic noise from several sources is known to interfere with touch sensing functions resulting in degraded quality of service (QoS). Many touch sensing implementations have built-in mechanisms that use avoidance and mitigation strategies. In isolation, these mechanisms are not very efficient or effective because these mechanisms make assumptions about the presence and characteristic of the environmental factors that may interfere with touch sensing.